


What you deserve.

by Kaorukeehl



Category: Undertale (Video Game)
Genre: Anger, Hatred, Hurt, Magic, Violence, mentioned child abuse
Language: English
Status: Completed
Published: 2017-11-12
Updated: 2017-11-12
Packaged: 2019-02-01 12:04:32
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 3,637
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12704637
Author URL: https://archiveofourown.org/users/Kaorukeehl/pseuds/Kaorukeehl
Summary: Where in one place things are happy and nice it may not be true in another place. Sometimes the darkest things could be happening to those we care about and we may not know it until it's too late. Luckily Undyne and Gaster find out about this bad thing going and now they have to save the two or they will end up dead. Dead by the hands of the man that was supposed to be their father.





	What you deserve.

“So this is their past.” Undyne glances around the area taking it in. She had agreed to try out Alphys’s time machine and she found herself here. She has her hair up in her usual ponytail and is wearing a black tank top with jeans and brown boots with the top part folded over.

This is where she met Gaster who greeted her kindly especially when he learned that she knew his sons.

“Yes. They are wonderful.” Gaster confirms. He is wearing a black lab coat with a white turtle neck underneath and black pants with dress shoes. His hands have a hole in the middle each and he has some scars on his face. He has one above his eye causing it to not open properly and one below his other eye connecting it to his mouth. “And I must say I am proud of them.” 

“I’m glad to hear that. They truly are something special after all.” Undyne agrees smiling as well along with Gaster. 

“That they are.” Gaster agrees and they make it to a machine. “This is a work in progress but perhaps this would be a good time to test it.” He begins clicking around on a control panel. “It should be able to take you back to your time and it’ll let me know if it works.”

“If not Alphys is most likely working to open the portal back to my time anyways.” Undyne assures him slightly waving it off. “By the way are the two the same as how I know them? I mean Sans likes to be lazy and he loves telling puns. He even sleeps on the job. He’s a lot stronger and smarter than he looks though. Papyrus may not be as smart but he isn’t stupid. He is strong too and wishes to be in the royal guard. Only Sans can put him to sleep and he’s really really kind.”

“Ah yes that sounds like him.” Gaster confirms with a chuckle closing his eyes for a moment as he does so. “Though I can get Papyrus to sleep as well. Sans is lazy yes but he’s willing to do work that is needed. He sometimes uses his joking as a way to communicate his feelings though. It’s something you pick up on after a bit.”

“Yeah. Sans isn’t big on showing his emotions.” Undyne agrees then Gaster hits a button.

The machine springs to life almost sounding like a purring cat.

The two watch waiting for the results anxious and nervous. They watch as a portal is opened and let out a breath they didn’t know they were holding. 

But that’s when two small objects come through the portal dropping them onto the floor. 

Gaster And Undyne blink in confusion and share a glance before turning back to the other two.

The portal closes leaving the two on the floor.

The two are a pair of kids, Papyrus and Sans, yet something looks off. They are wearing worn and beat up clothes. They also seem to be possibly injured with Papyrus having a part of his arm wrapped in bandages, plus Sans having a crack coming from his eye to the side of his skull. They look to Undyne and Gaster with caution and fear.

“Well not exactly what I was expecting.” Undyne admits slightly scratching her head at this.

“It’s alright. Nothing will happen.” Gaster assures the two with a gentle loving smile. “It would appear my machine opened a portal to your world. Are you two alright? May I ask where you got your injuries?” He tries to move closer wishing to inspect their injuries in the hopes of healing them. 

However he stops as the two scramble back in terror not daring to get to their feet.

Papyrus even ducks down behind Sans in fright while Sans lets him.

“Oh dear. Why are you frightened?” Gaster questions confused and worried. He slightly reaches out towards the two not fully sure what to do. He wants to help but he doesn’t think the two will allow him any closer. He frown trying to figure out why. Though he knows that the two are not from his world it still breaks his heart to see their terror of him. But why would they be scared of him. “Come now. I won’t... Hurt you....” He trails off as he finds it dawning upon him and his breath catches in his throat. 

Undyne turns to Gaster confuses and questioning in the hope that he was onto something. 

“Oh no.” Despite being a skeleton Gasters face manages to pale and his hands clench rather tightly into fists. 

“What is it?” Undyne inquires wanting to know what has just crossed through Gasters mind. 

“Please not again.” Papyrus’s whimper causing the two to look to him. He’s still hiding behind Sans and his hands are now on his skull. His eyes are shut rather tightly while his fingers try to grip his skull. “We’re sorry! Whatever it is that we did! Please. Please don’t. Don’t do it again.” His words fall into unintelligible words mixed with whimpers.

Sans reaches one hand back gently placing it on Papyrus’s uninjured arm for comfort. 

“Sadly It would appear that the me in the other world is not as pleasant or loving.” Gaster informs Undyne who glances to him.

Undynes war fins drop upon hearing this. “You don’t mean that this other you is...” She trails off not really even sure she wants to finish that thought. 

Gaster closes his eyes letting out a heavy sigh. “Yes. It would appear that in this other universe I am abusive.” His hands are clenched so tight that he almost makes himself bleed. 

Undynes breath catches in her throat upon hearing this confirmation. Her own hands balling up into right fists of anger.

“Even if I know I’m not the same as this other me.” Gaster begins with a growl of rage. “I can’t help but feel disgusted and angry with myself.” 

Undyne unclenches one of her hands putting it upon Gasters shoulder. “Even in the short amount of time I’ve been here I know that you wouldn’t do that. This other you is the one to blame.” 

“Yes.” Gaster nods and he looks the two boys over for a moment. He sighs sadly before turning to meet Undynes eye. “I don’t think that they’ll let me anywhere near them right now. Not without being terrified. Could you check them? I’ll need to approach slowly if I want to get close. But even then they’ll be terrified.” 

“It isn’t your fault but yes. I’ll check on them and you slowly move closer.” Undyne agrees with a nod to that. “We need to try to show them that you’re not going to hurt them here.” 

Gaster nods in agreement and so Undyne turns to the boys moving closer. 

They are weary but allow her to move closer to them. They watch her carefully as she even crouches by them. 

“It’s okay. Everything will be alright now.” She assures them with a gentle smile and reaches towards them. She makes sure that they can see her hand though she almost pauses when they flinch away. She is almost touching Sans as the two shut their eyes as if expecting to be struck. She places her hand gently on top of Sans’s skull.

Sans’s eyes snap open in shock and he slightly glances up to Undyne who gives him a gentle smile. 

“It’s alright. You’re doing good.” Undyne praises them as they look at her in shock and confusion. “Never been complimented before huh?” She wonders out loud. “It feels good doesn’t it? Well let me take a look at your injuries.” He moves her hand gently brushing it by the crack that Sans has.

Sans flinches in which Undyne pulls her hand back enough to not be touching him.

“Still stings doesn’t it? Hold on I know some healing magic.” She places her hand over the crack in which her hand glows green. She pulls away letting the green fade once done.

The crack nowhere to be seen.

She turns to Papyrus and offers her hand to him. “Will you let me take a look at you.” 

Seeming to understand that Undyne will not harm them, Sans uses a hand to gently encourage Papyrus towards Undyne. 

Undyne removes the bandages to find a real nasty crack that almost broke his arm. She frowns at it but places a gentle hand over it. She can’t help but flinch when Papyrus yelps slightly from the sting. “It’ll be over soon.” She lets her hand glow green until she has repaired Papyrus’s arm. She removes her hand but right after Sans pulls Papyrus close. She turns to see that Gaster had been moving closer while Undyne was healing the two. She looks to the two with an assuring smile. “There is no need to be afraid.” She informs them. “Hes not like your Gaster at all. He’d never harm you.” 

Gaster crouches down hoping to not be as intimidating than towering over them when standing. “You’re safe.” He reaches towards them slowly and the two try to scramble back.

Undyne stops them and so the two close their eyes expecting pain. 

Gaster places a hand on the top of Sans’s then Papyrus’s skulls. He gives them a gentle rub there as they crack open an eye each. 

Their gazes hold a mix of confusion, fear and surprise. 

Gaster just smiles gently at them trying to keep them assured. “That’s wonderful. You both are such good monsters.” He tells them gently and they open both eyes not sure what’s going on.

They all turn as a portal opens and Alphys steps in holding a remote.

She has her usual clothes on including her lab coat. “U-Undyne! We can open the portal and head h-home now.” She pauses to glance at the scene before her.

Undyne gets up and Gaster lets go of the two boys. “Alphys.” She begins getting Alphys to look to her. “I need you to watch these two right now.” She gestures a hand to the young Papyrus and Sans. “I have some business to attend to in another world. It appears a certain monster refuses to treat them right.”

“I’m coming too!” Gaster gets up and the girls turn to him. “No one hurts them and gets away with it. We can use my machine to get to their world and show the monster what happens when you follow his path.”

Undyne smiles glad to hear the other being on board.

“O-Okay.” Alphys agrees with her stutter. “A-And Undyne?”

“Yeah?” Undyne turns meeting her eyes.

“M-Make him truly pay. Okay?”

Undyne grins and nods before cracking her knuckles. “Oh don’t worry I will.” She assures her girlfriend. “I will.” 

The two boys are sent over to Alphys while Dadster Gaster boots up the machine again.

“T-There. Nice and safe.” Alphys speaks softly to the two as she carefully puts her arms around them. She looks up as the portal is opened with Dadster and Undyne facing it. “G-Good luck.”

Undyne turns flashing Alphys a thumbs up before following Dadster into the portal. She glances around along with the other as they try to see if the other Gaster is close by.

“My my what is this?”

The two turn to now be facing another Gaster not noticing the portal has closed.

Not that it mattered as Dadster had made a remote to access the machine just in case. 

“Where did you come from?” Gaster questions in interesting glancing around as if trying to spot their point of entry. 

“That isn’t what you need to know.” Dadster tells Gaster who turns to him as he cracks his knuckles. He doesn’t want to let Gaster know in fear that it will mean that the other will get to the boys again. “What you do need to know is that we’re here to hand you your ass on a silver platter.”

Gaster looks at them with a rather unamused look that could be considered a glare. “Oh? And what makes you think you can win against me? I’ll beat you to the ground pathetic piece of trash.”

Dadster snarls as he can only imagine that the Sans and Papyrus from here have probably heard that before.... And found out that Gaster wasn’t lying when he said such a thing. He throws a hand out sending out a black tentacle heading straight for Gaster.

Gaster jumps out of the way then summons his Gaster blaster firing it to destroy the tentacle. He turns as Undyne appears at his side slashing her magic made spear in his direction. He raises his arm taking the hit even as it damages his sleeve. He then uses the moment to move his hand swiftly to send Undyne flying so she crashes into the wall. He turns just as he fires his Gaster blaster in the direction of Dadster.

Dadster manages to block it with his black tentacles that cover the front of him. He then sends them flying towards Gaster.

Gaster summons a bone and slashed the tentacles before any of them could reach him. He pauses after slashing the last one to look back.

A spear is heading straight for him from behind.

Gaster turns and uses his bone attack to knock it away sending it flying.

The spear is sent through the roof of the building off to somewhere else.

Gaster helps as he is suddenly struck in the back. He leaps away before turning to see Dadster standing there with an enraged glare. He glances to his back noticing three bones stuck in his back. “Hm. You little pieces of shits really think that such a thing would stop me?” He turns to glare at Dadster with laughter in his tone. “How pathetic.” He throws one arm out summoning a bunch of bones. “Let me show you how to truly fight.” He points his hand towards Dadster causing the bones to fly towards him at a great speed.

“Don’t forget about me you fucker!” Undyne charges towards Gaster a spear in each hand. She has herself surrounded by a bunch of spears as well.

All pointing in Gasters direction.

Gasters eyes are half open definitely super unimpressed. “You know I almost did forget about you.” He admits in a bored tone. “You’re not very memorable.” He watches as Undyne flies towards him along with her spears. “Not that it matters.” He summons a black tentacle that swats the spears away before swiping at her.

Undyne responds by swinging her spear at the tentacle cutting it. She smirks at Gaster and just after one spear from behind slams into a bone in his back.

This causes the bone to dig further into Gasters back. 

Gaster arches his back slightly at the pain and his tentacle as well as Gaster blaster vanish. He snarls his unamused look narrowing into that of a raged look. “Oh that’s fucking it!”

Undyne uses his distraction to slam a hard punch to Gasters jaw hearing a satisfying snap. She knows that she had broken his jaw and damn does it feel good. 

Gaster stumbles before turning with a death glare. His eyes lit up with purple magic like Dadsters eyes. “You useless brat!” He snarls before he is suddenly attacked from behind.

Dadster has summoned a bone and swings it at Gasters leg. He uses the moment that Gaster is one one knee to lock it against Gasters neck. He applies pressure as Gasters hands grip it. He doesn’t care if he hurts his version of him at all. “Let me tell you something.” He growls where Gasters ear should be. “You are the only worthless and useless piece of trash I have ever met.” 

Gaster simply laughs. “As much as your delusions are entertaining I have some more important things to be doing.” He summons his Gaster blaster aiming right at both of them from behind.

“You fire and you hurt yourself idiot.” Dadster warns in a rather dark tone already knowing that Gaster plans on blasting them both. 

This statement only makes Gaster laugh even harder. “That’s what you think! I trained my magic to not harm me!” His smirk widens in victory. “Say goodbye.” He is about to unleash the Gaster blasters beam when suddenly there is a slash cutting it in half.

Undyne no longer has two spears as the other is in the ground right where the Gaster blaster was. She smirks at Gaster who glares at her. She runs forward and slams a punch right into the middle of his face. She can hear the cracking of bone as she gives him some cracks on his face. She pulls back her fist that has some blood on it from where blood drips from the cracks. “You deserve every bit of this.” She snarls at him before slamming another fist into Gasters face this time hitting the top of his skull. “Every. Fucking. Blow.” She slams a fist into Gasters rib cage managing to break about three of his ribs cleanly off. “For everything you’ve done.”

“They’re children.” Dadster adds with a snarl glaring at Gaster with hate and rage. “And yet you made them suffer. You made them love through hell. Well now how does it feel to be on the receiving end of such things?” 

Gasters hand shoots out towards Undyne before either knee it. He grabs her by the throat and laughs. “This is truly pathetic. You really think that you’ve won this? Oh my you are so much more stupider than I thought? Why should any of this matter to you?” He tightens his grip on Undynes throat.

Undyne sends a bunch of spears into Gasters arm but Gaster doesn’t let go. 

Dadster even tries to yank him back to force him to let go but not even that works. 

“They aren’t worth anything to the world. It doesn’t matter what happens to them. No one cares.” Gasters states as if that is pure fact.

“That’s where you’re wrong.” Dadster responds with a growl in his tone before letting go of one side of the bone. He summons another and slams it into Gasters side harshly. “Even if you think that no one cares we do. And you will never lay a finger on them again. You disgust me.” He pushes it further in causing the tip to tap against Gasters soul.

Gaster gasps at the jab and feels weak in the knees from the harsh damage. He releases Undyne unable to hold her anymore.

“One more thing.” Undyne hisses just after she lands on her feet on the ground. She reaches over putting both hands on the arm that had held her. She gives a jerk snapping the arm completely in half. “Now you will understand their pain even more.” She growls enjoying the pained sounds coming from Gaster.

“You’re lucky we don’t kill.” Dadster adds in a low dangerous tone before both Undyne and Dadster release Gaster. He slams a foot down into Gasters leg breaking it like Undyne broke his arm. “You got what you deserved.” He informs Gaster who lays there on the ground bleeding and in pain. “You will never see those two again. Ever.” He speaks before he turns away and with Undyne following the two head away. He doesn’t want Gaster to see them leave through the portal. He makes it activate and they head back to where Alphys and the boys are waiting. 

Alphys has them curled up against her asleep like they haven’t slept well in awhile. 

Undyne smiles at the sight unable to help but imagining their own kids being there instead of the brothers. 

“H-How’d it go?” Alphys asks a little quietly not wishing to awaken the brothers just yet. 

“We beat him.” Undyne announces proudly though she keeps her voice down. “That fucking bastard will never harm them again.”

Dadster glances away thoughtfully though he gives a sad sigh causing Undyne to look to him. 

“What’s up?” Undyne inquires and Dadster looks to her.

“I will need to take them to their world. They aren’t from here so they don’t belong.” Dadster begins but continues before Undyne can protest. “I will take them to the Asgore in that world and explain what has been happening. Everything should be taken care of from there.”

Undyne pauses and turns to glance to the brothers as they sleep peacefully. She thinks about it for a few moments before turning back to Dadster. “Well why not?” She questions the other. “I mean what if he was right? What if no one there actually cares about them?” She points out and Dadster glances away sadly in thought. “They’d only end up right back where they started. And I’m sure we’ve left that Gaster enraged enough that he’d kill them the moment he got his hands on them. We don’t know much about that world or if even Asgore is the same as we know him. He might lie to us saying that he’ll handle it then hand them back to Gaster once we’re gone.”

“You are correct.” Dadster sighs then he smiles and gives Undyne a look of determination with a nod. “Alright. I’ll keep them and give them the family life that they deserve.”

Undyne smiles at him. “I know you will.”

And so Alphys activates the portal to get them home leaving the boys with Dadster.

Dadster turns to look to the boys that Alphys had laid gently on the floor. He knows it’ll be a lot of work to help them but he’s willing to do whatever it takes to heal them. “Welcome to your new home. My sons.”

The end.

**Author's Note:**

> Just a fun little story I wanted to do after some discussions with my friend Dragonsrule18. Dadster belongs to my friend. I hope Dadster was the way you thought he’d be friend.
> 
> Gaster is indeed an abusive one that I made for some of my stories. His specific one comes from The signs of the damaged, and some others ones that at the time of me posting this are works in progress. Including Never again and a currently unnamed fanfic.


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